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## Page 1 of 24 Note: This guidance is for facilities pe rforming a BART analysis. The MPCA used modeling to determine which units contribute to visibility impairment in a Class I area and are therefore “subject to BART”. The MPCA requests facilities with emission units that are subject to BART to complete a BART analysis within 6 months of notification. Section IV of EPA’s “Guidelines for BART Determinations under the Regional Haze Rules” [40 CFR Part 51, Appendix Y] is repr inted below. The EPA’s Guidelines were written for states to use in making BART determinati ons. The MPCA is asking facilities to follow these Guidelines in completing their BART analysis. The MPCA has inserted notes (in grey boxes) into the Guidelines text below to clarify expectations for a BART analysis. The MPCA will use the BART analysis to make the actual BART determinations, subject to EPA approval. In each step of the analysis, facilities are asked to clearly document rationale, data sources, etc. Facilities are requested to submit the BART analysis using the format in Attachment 3.

IV. The BART Determination: Analysis of BART Options This section describes the process for the analysis of control options for sources subject to BART.

A. What factors must I address in the BART review? The visibility regulations define BART as follows: Best Available Retrofit Technology (BART) means an emission limitation bas ed on the degree of reduction achievable through the application of t he best system of continuous emission reduction for each pollutant which is emitted by . . . [a BART-eligible source]. The emission limitation must be established, on a case-by-case basis, taking into consideration the technology available, the costs of compliance, t he energy and non-air quality environmental impacts of compliance, any pollution control equipment in use or in existence at the source, the remaining useful life of the source, and the degree of impr ovement in visibility which may reasonably be anticipated to result from the use of such technology. The BART analysis identifies the best system of cont inuous emission reduction taking into account: (1) The available retrofit control options, (2) Any pollution control equipment in use at the source (which affects the availability of options and their impacts), (3) The costs of compliance with control options, (4) The remaining useful life of the facility, (5) The energy and non-air quality environmental impacts of control options (6) The visibility impacts analysis. B. What is the scope of the BART review? Once you determine that a source is su bject to BART for a particular pollutan t, then for each affected emission unit,

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## Page 2 of 24 you must establish BART for that pollutant. The BART dete rmination must address air pollution control measures for each emissions unit or pollutant emitting activity subject to review. Example: Plantwide emissions from emission units within the listed categories t hat began operation within the “time window” for BART 11 are 300 tons/yr of NO X , 200 tons/yr of SO 2 , and 150 tons/yr of primary particulate. Emissions unit A emits 200 tons/yr of NO X , 100 tons/yr of SO 2 , and 100 tons/yr of primary particulate. Other emission units, units B through H, which began operating in 1966, contribute lesser amounts of each pollutant. For this example, a BART review is required for NO X , SO 2 , and primary particulate, and control options must be analyzed for units B through H as well as unit A.

11 That is, emission units that were in existence on August 7, 1977 and which began actual operation on or after August 7, 1962.

C. How does a BART review relate to Maximum Achievable Contro l Technology (MACT) Standards under CAA section 112, or to other emissi on limitations required under the CAA? For VOC and PM sources subject to MACT standards, St ates may streamline the analysis by including a discussion of the MACT controls and whether any major new technologies have been developed subsequent to the MACT standards. We believe that there are many VOC and PM sources that are well controlled because they are regulated by t he MACT standards, which EPA developed under CAA section 112. For a few MACT standards, this may also be true for SO 2 . Any source subject to MACT standards must meet a level that is as stringent as the best-controll ed 12 percent of sources in the industry. Examples of these hazardous air pollut ant sources which effectively control VOC and PM emissions include (among others) secondary lead faci lities, organic chemical plants subject to the hazardous organic NESHAP (HON), pharmaceutical production facilities, and equipment leaks and wastewater operations at petroleum refineries. We be lieve that, in many cases, it will be unlikely that States will identify emission controls more stringentthan the MACT standards wi thout identifying control options that would cost many thousands of dolla rs per ton. Unless there are new technologies subsequent to the MACT standards which would lead to cost-effective increases in the level of control, you may rely on the MACT standards for purposes of BART. We believe that the same rationale also holds true for emissions standards developed for municipal waste incinerators under CAA section 111(d), and for many NSR/PSD determinations and NSR/PSD settlement agreements. However, we do not belie ve that technology determinations from the 1970s or early 1980s, including new source performance standards (NSPS), should be considered to represent best control for existing sources, as best control levels for recent plant retrofit s are more stringent than these older levels. Where you are relying on these standards to represent a BART level of control, you should provide the public with a discussion of whether any new technologies have subsequently become available. MPCA Note: The MPCA intends to streamline the analysis of PM and VOC sources subject to MACT standards in a BART analysis. The MPCA agrees with U.S. EPA’s assertion that it is unlikely that states will identify controls more stringent than the MACT standards without incurring much higher costs. Therefore, the MPCA will rely on MACT standards to represent BART level of control for those visibility-impairing pollutants addressed by the MACT standard unless there are new technologies subsequent to the MACT standards, which would lead to cost-effective increases in the level of control. For example, if a BART-eligible emissions unit emits PM10 and NOx and the unit is subject to a MACT limit for PM10, then a full BART analysis need only address NOx. If you have units emitting visibility-impairing pollutants t hat are addressed by a MACT standard(s), then please list those units or groups of units in se ction III of the BART analysis (see Atta chment 3). Please include the MACT standard, the limit imposed on the unit by the MACT standar d, the MACT limit converted into a pounds/day value, and document your rationale as to why the MACT standar d represents BART. No further analysis is needed of those units for that visibility-impairing pollutant. If you believe that recent application of a BAC T or NSPS standard represents BART for an emission unit, please consult with MPCA staff early in the BART analysis proc ess for further guidance on the expected level of analysis.

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## Page 3 of 24 D. What Are the Five Basic Step s of a Case-by-Case BART Analysis? The five steps are: STEP 1—Identify All 12 Available Retrofit Control Technologies,

12 In identifying “all” options, you mu st identify the most stringent opti on and a reasonable set of options for analysis that reflects a comprehensive list of avai lable technologies. It is not necessary to list all permutations of available control levels that exist for a given technology—the list is complete if it includes the maximum level of control each tech nology is capable of achieving. STEP 2— Eliminate Technically Infeasible Options,

STEP 3— Evaluate Control Effectiveness of Remaining Control Technologies, STEP 4— Evaluate Impacts and Document the Results, and STEP 5—Evaluate Visibility Impacts. 1. STEP 1: How do I identify all availabl e retrofit emission control techniques? 1. Available retrofit control options ar e those air pollution control technologies with a practical potential for application to the emissions unit and the regulated pollutant under eval uation. Air pollution control technologies can include a wide variety of available methods, systems, and techniques for control of the affected pollutant. Technologies required as BACT or LAER are available for BART purpos es and must be included as control alternatives. The control alternatives can include not onl y existing controls for the source category in question but also take into account technology transfer of controls that have been applied to similar source categories and gas streams. Technologies which have not yet been applied to (or permitted for) full scale operations need not be considered as available; we do not expect the source owner to purchas e or construct a process or control device that has not already been demonstrated in practice. 2. Where a NSPS exists for a source category (which is t he case for most of the categories affected by BART), you should include a level of control equivale nt to the NSPS as one of the control options 13 The NSPS standards are codified in 40 CFR part 60. We note t hat there are situations where NSPS standards do not require the most stringent level of available control for all sources within a category. For example, post-combustion NO X controls (the most stringent controls for stationary gas turbines) are not required under subpart GG of the NSPS for Stationary Gas Turbines. However, such controls must still be c onsidered available technologies for the BART selection process.

13 In EPA's 1980 BART guidelines for reasonably attributable visibility impairment, we concluded that NSPS standards generally, at that time, represented the best level sources could install as BART. In the 20 year period since this guidance was developed, there have been advances in SO 2 control technologies as well as technologies for the control of other pollutants, confirmed by a numbe r of recent retrofits at Western power plants. Accordingly, EPA no longer concludes that the NSPS level of controls automatically represents “the best these sources can install.” Analysis of the BART factors could re sult in the selection of a NSPS level of control, but you shou ld reach this conclusion only after considering the full range of control options. 3. Potentially applicable retrofit control al ternatives can be categorized in three ways. • Pollution prevention: use of inherently lower-emitti ng processes/practices, including the use of control techniques ( e.g., low-NO X burners) and work practices that prevent emissions and result in lower “production-specific” emissions (note that it is not our intent to dire ct States to switch fuel forms, e.g., from coal to gas),

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## Page 4 of 24 • Use of (and where already in place, improvement in the performance of) add-on controls, such as scrubbers, fabric filters, thermal ox idizers and other devices that cont rol and reduce emissions after they are produced, and • Combinations of inherently lower-emitting processes and add-on controls.
MPCA Note: At a minimum, taconite plants should consid er the control technologies and work practices/operational changes in the table below as retr ofit control alternatives for thei r BART-eligible indurating furnaces:

Pollutant Description Comments SCR IFGR Burners Low-NOx burners Including ultra-low NOx burners Ported Kiln Only for rotary kilns Control Technologies:

LoTOx NOx CEM Also investigate other forms of monitoring to ensure combustion efficiency NOx

Work Practices/ Operational Changes:

Alternative fuels Evaluate use of biomass as fuel High efficiency wet scrubber (> 90% removal) Low efficiency wet scrubber (> 50% removal) Control Technologies:

Lime/Limestone wet slurry scrubbing Look at various alternatives to enhance SO2 collection efficiency of existing web scrubbers SO 2

Work Practices/ Operational Changes: Alternative fuels

4. In the course of the BART review, one or more of the available control optio ns may be eliminated from consideration because they are demonstrated to be technicall y infeasible or to have unacceptable energy, cost, or non-air quality environmental impacts on a case-by-case (or si te-specific) basis. However, at the outset, you should initially identify all control optio ns with potential application to the emissions unit under review. 5. We do not consider BART as a requirement to redes ign the source when considering available control alternatives. For example, where the source subject to BART is a coal-fired electric generator, we do not require the BART analysis to consider building a natural gas-fired elec tric turbine although the turbine may be inherently less polluting on a per unit basis. 6. For emission units subject to a BART review, there will o ften be control measures or devices already in place. For such emission units, it is important to include control options that involve im provements to existing controls and not to limit the control options only to those measures that involve a complete replacement of control devices. Example: For a power plant with an existing wet scrubber, the current control efficiency is 66 percent. Part of the reason for the relatively low control effici ency is that 22 percent of the gas stream bypasses the scrubber. A BART review identifies options for improving the performance of the wet scrubber by redesigning the internal components of the scrubber an d by eliminating or reduc ing the percentage of the gas stream that bypasses the scrubber. Four control options are identified: (1) 78 percent control based upon improved scrubber performance while maintaini ng the 22 percent bypass, (2) 83 percent control based upon improved scrubber performance while r educing the bypass to 15 percent, (3) 93 percent control based upon improving the scr ubber performance while eliminating the bypass entirely, (this option

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## Page 5 of 24 results in a “wet stack” operation in which the gas leaving the stack is saturated with water) and (4) 93 percent as in option 3, with the addition of an indire ct reheat system to reheatthe stack gas above the saturation temperature. You must consider each of these four options in a BART analysis for this source. 7. You are expected to identify potentially applicable retrofit control technologies that represent the full range of demonstrated alternatives. Examples of general information sources to consider include: • The EPA's Clean Air Technology Center, which incl udes the RACT/BACT/LAER Clearinghouse (RBLC); • State and Local Best Available Control Technolog y Guidelines—many agencies have online information— for example South Coast Air Quality Management District, Bay Area Air Quality Management District, and Texas Natural Resources Conservation Commission; • Control technology vendors; • Federal/State/Local NSR permits and associ ated inspection/performance test reports;
• Environmental consultants; • Technical journals, reports and newsletters, air pollution control seminars; and

• The EPA's NSR bulletin board— http://www.epa.gov/ttn/nsr; • Department of Energy's Clean Coal Program—technical reports;

• The NO X Control Technology “Cost Tool”—Clean Air Markets Division Web page— http://www.epa.gov/airmarkets/ arp/nox/controltech.html; • Performance of selective catalytic reduction on c oal-fired steam generating uni ts—final report. OAR/ARD, June 1997 (also available at http://www.epa.gov/airmarket s/arp/nox/cont roltech.html ); • Cost estimates for selected applications of NO X control technologies on stationary combustion boilers. OAR/ARD June 1997. (Docket for NO X SIP Call, A–96–56, item II–A–03); • Investigation of performance and cost of NO X controls as applied to group 2 boilers. OAR/ARD, August 1996. (Docket for Phase II NO X rule, A–95–28, item IV–A–4); • Controlling SO 2 Emissions: A Review of Technologi es. EPA–600/R–00–0 93, USEPA/ORD/NRMRL, October 2000; and

• The OAQPS Control Cost Manual. You are expected to compile appropriate info rmation from these information sources. 8. There may be situations where a specif ic set of units within a fenceline constitutes the logical set to which controls would apply and that set of units may or may not all be BART- eligible. (For example, some units in that set may not have been constructed between 1962 and 1977.) 9. If you find that a BART source has controls already in pl ace which are the most stringe nt controls available (note that this means that all possible improvements to any cont rol devices have been made), then it is not necessary to comprehensively complete each following step of the BART analys is in this section. As long as these most stringent controls available are made federally enforceable for t he purpose of implementing BART for that source, you may skip the remaining analyses in this section, including the visib ility analysis in step 5. Likewise, if a source commits to a BART determination that consists of t he most stringent controls available, then there is no need to complete the

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## Page 6 of 24 remaining analyses in this section. MPCA Note: The MPCA will consider on a case-by-case basis whether a BACT determination or NSPS limit for a particular pollutant at a BART-eligible unit satisfies BART requirements. The MPCA will take into account the age of the BACT determination or NSPS limit, whether any new technologies have subsequently become available (including work practices that reduce emissions), and t he visibility analysis that was performed for the BACT determination. The MPCA encourages facilities to cons ult with MPCA staff during the development of their BART analysis if they believe a BACT determination or NSPS limit represents BART and t hat no further analyses are required for a particular visibility-impairing pollutant. 2. STEP 2: How do I determine whether the options identified in Step 1 are technically feasible? In Step 2, you evaluate the tec hnical feasibility of the cont rol options you identified in Step 1. You should document a demonstration of technical infeasibility and should explai n, based on physical, chemical, or engineering principles, why technical difficulties would preclude the successful use of the control option on the em issions unit under review. You may then eliminate such technically infeasible contro l options from further consideration in the BART analysis. In general, what do we mean by technical feasibility? Control technologies are technically feasible if either (1 ) they have been installed and operated successfully for the type of source under review under similar conditions, or (2) the technology could be applied to the source under review. Two key concepts are important in determining whether a technology could be applied: “availability” and “applicability.” As explained in more detail below, a tech nology is considered “available” if the source owner may obtain it through commercial channels, or it is otherwise available within th e common sense meaning of the term. An available technology is “applicable” if it can reas onably be installed and operated on the source type under consideration. A technology that is availa ble and applicable is technically feasible. What do we mean by “available” technology? 1. The typical stages for bringing a control technology concept to reality as a commercial product are: • Concept stage; • Research and patenting; • Bench scale or laboratory testing; • Pilot scale testing; • Licensing and commercial demonstration; and

• Commercial sales. 2. A control technique is considered available, within t he context presented above, if it has reached the stage of licensing and commercial availability. Similarly, we do not ex pect a source owner to conduct extended trials to learn how to apply a technology on a totally new and dissimilar source type. Consequently, you would not consider technologies in the pilot scale testing stages of development as “available” for purposes of BART review. 3. Commercial availability by itself, however, is not necessa rily a sufficient basis for concluding a technology to be applicable and therefore technically feasible. Technical feasibility, as determined in St ep 2, also means a control option may reasonably be deployed on or “applicab le” to the source type under consideration. Because a new technology may become available at various points in time during the BART analysis process, we believe that guidelines are needed on when a technology must be considered. For example, a technology may become available during the public comment period on the State's rule development process. Likewise, it is

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## Page 7 of 24 possible that new technologies may become available after the close of the Stat e's public comment period and before submittal of the SIP to EPA, or during EPA's review process on the SIP submittal. In order to provide certainty in the process, all technologies should be considered if available before the close of the State's public comment period. You need not consider technologi es that become available after this dat e. As part of your analysis, you should consider any technologies brought to your attent ion in public comments. If you disagree with public comments asserting that the technology is available, you should provide an explanation for the public record as to the basis for your conclusion.
MPCA note: For the purpose of the BAR T analysis, please consider all availa ble technologies as of the date of submittal of the BART analysis. What do we mean by “applicable” technology? You need to exercise technical judgment in determining whether a control alternative is applicable to the source type under consideration. In general, a commercially availabl e control option will be presumed applicable if it has been used on the same or a similar source type. Absent a show ing of this type, you evaluate technical feasibility by examining the physical and chemical c haracteristics of the pollutant-bearing gas stream, and comparing them to the gas stream characteristics of the source types to which the technology had been applied previously. Deployment of the control technology on a new or existing source with si milar gas stream characteristics is generally a sufficient basis for concluding the technology is technically feasib le barring a demonstration to the contrary as described below. What type of demonstration is required if I conclude that an option is not technically feasible? 1. Where you conclude that a control opti on identified in Step 1 is technically infeasible, you should demonstrate that the option is either commercially unavaila ble, or that specific circumstances pr eclude its application to a particular emission unit. Generally, such a demonstration involves an evaluation of the characterist ics of the pollutant-bearing gas stream and the capabilities of the technology. Alte rnatively, a demonstration of technical infeasibility may involve a showing that there are unresolvable technical difficulties with applying the control to the source ( e.g. , size of the unit, location of the proposed site , operating problems related to specificcircumstances of the source, space constraints, reliability, and adverse side effects on the re st of the facility). Where the resolution of technical difficulties is merely a matter of increased cost, you should consider the technology to be technically feasible. The cost of a control alternative is considered later in the process.

2. The determination of technica l feasibility is sometimes influenced by recentair quality permits. In some cases, an air quality permit may require a certain level of control, but the level of control in a permit is not expected to be achieved in practice ( e.g. , a source has received a permit but the project was canceled, or every operating source at that permitted level has been physically unable to achieve compliance with the limit). Where this is the case, you should provide supporting documentation showing why such lim its are not technically feas ible, and, therefore, why the level of control (but not necessarily the technology) ma y be eliminated from further co nsideration. However, if there is a permit requiring the applicati on of a certain technology or emission limit to be achieved for such technology, this usually is sufficient justification for you to assume the technical feasibility of that technology or emission limit.
MPCA note: Air emission permits are available online at http://www.pca.state.mn.us/ air/permits/issued/index.html

. 3. Physical modifications needed to resolve technical obst acles do not, in and of themselv es, provide a justification for eliminating the control technique on the basis of technical infeasibility. Ho wever, you may consider the cost of such modifications in estimating costs. This, in turn, may form the basis for eliminating a control technology (see later discussion). 4. Vendor guarantees may provide an indication of commercial availability and the technical feasibility of a control technique and could contribute to a determination of technica l feasibility or technical infeasibility, depending on circumstances. However, we do not consider a vendor guar antee alone to be sufficient ju stification t hat a control option will work. Conversely, lack of a vendor guarantee by itself does not present suffi cient justification that a control option or an emissions limit is technically infeasib le. Generally, you should make decisions about technical feasibility based on chemical, and engineering analyses (as discussed above), in conjunction with information about

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## Page 8 of 24 vendor guarantees. 5. A possible outcome of the BART procedures discussed in t hese guidelines is the eval uation of multiple control technology alternatives which result in essentially equiva lent emissions. It is not our intent to encourage evaluation of unnecessarily large numbers of control alternatives for every emissions unit. Consequently, you should use judgment in deciding on those alternatives for which yo u will conduct the detailed impacts analysis (Step 4 below). For example, if two or more control techniques result in c ontrol levels that are essentia lly identical, considering the uncertainties of emissions factors and other parameters pe rtinent to estimating performance, you may evaluate only the less costly of these options. You should narrow the sco pe of the BART analysis in this way only if there is a negligible difference in emissions and energy and non-air quality environmental impacts between control alternatives. 3. STEP 3: How do I evaluate technically feasible alternatives? Step 3 involves evaluating the control effectiveness of all th e technically feasible control alternatives identified in Step 2 for the pollutant and emissions unit under review. Two key issues in this process include: (1) Making sure that you express the degree of cont rol using a metric that ensures an “apples to apples” comparison of emissions performance levels among options, and (2) Giving appropriate treatment and consideration of control techniques that can operate over a wide range of emission performance levels. What are the appropriate metrics for comparison? This issue is especially important wh en you compare inherently lower-polluting processes to one another or to addon controls. In such cases, it is generally most effective to express em issions performance as an average steady state emissions level per unit of product produced or processed. Examples of common metrics:

• Pounds of SO 2 emissions per million Btu heat input, and

• Pounds of NO X emissions per ton of cement produced.
MPCA Note: For EGUs, please provide compare emissions in units of pounds per million Btu heat input. For indurating furnaces at taconite fac ilities, please compare emissions as fo llows: for SO2 and NOx use lb/ hour. All emissions should also be provided on a lb/day basis as these are the units that will be used for modeling purposes. In evaluating the reductions attainable from the use of a NOx CEM on indurating furnaces to improve combustion practices, you may assume a 20 percent reduction unle ss you have information to support another value. The MPCA believes that potential reductions range from 15 to 35 percent due to improved operational information. How do I evaluate control techniques with a wide range of emission performance levels? 1. Many control techniques, including both add-on controls and inherently lower polluting processes, can perform at a wide range of levels. Scrubbers and high and low efficien cy electrostatic precipitators (ESPs) are two of the many examples of such control techniques that can perform at a wide range of levels. It is not our intent to require analysis of each possible level of efficiency for a control technique as such an analysis would result in a large number of options. It is important, however, that in an alyzing the technology you take into account the most stringent emission control level that the technology is capable of achieving. You should consider recent regulatory decisions and performance data ( e.g. , manufacturer's data, engineering es timates and the experience of other

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## Page 9 of 24 sources) when identifying an emissions performance level or levels to evaluate. 2. In assessing the capability of the cont rol alternative, latitude exists to cons ider special circumstances pertinent to the specific source under review, or regarding the prior appl ication of the control alternat ive. However, you should explain the basis for choosing the alternate level (or range) of control in the BART analysis. Without a showing of differences between the source and other sources that have achieved more stringent emissions limits, you should conclude that the level being achieved by those other sources is representative of the achievable level for the source being analyzed. 3. You may encounter cases where you may wish to evaluate other levels of control in addition to the most stringent level for a given device. While you must consider the mo st stringent level as one of the control options, you may consider less stringent levels of contro l as additional options. This would be useful, particularly in cases where the selection of additional options would have widely varying costs and other impacts. 4. Finally, we note that for retrofitting existing sources in addressing BART, you should consider ways to improve the performance of existing control devices, particularly when a c ontrol device is not achievi ng the level of control that other similar sources are achieving in practice with the sa me device. For example, you should consider requiring those sources with electrostatic precipitators (ESPs) perfo rming below currently achievable levels to improve their performance. 4. STEP 4: For a BART review, what impacts, am I expected to calculate and report? What methods does EPA recommend for the impacts analysis? After you identify the available and technically feasible control technology options, you are expected to conduct the following analyses when you make a BART determination: Impact analysis part 1: Costs of compliance, Impact analysis part 2: Energy impacts, and Impact analysis part 3: Non-air quality environmental impacts. Impact analysis part 4: Remaining useful life.
In this section, we describe how to conduct each of t hese three analyses. You are responsible for presenting an evaluation of each impact along with appropriate supporti ng information. You should discuss and, where possible, quantify both beneficial and adverse impacts. In general, th e analysis should focus on the direct impact of the control alternative. MPCA Note: The Guidelines do not explicitly mention ho w to deal with collateral increases in another regulated pollutant as a result of a control alternative. For example, use of furnace sorbent injection to control SO2 in a boiler could result in an increase in PM emissions. This incr ease could trigger other air quality requirements such as NSPS or NSR. The MPCA asks that you identify any coll ateral increases in other re gulated pollutants in your analysis. If you select a control that has collateral increases as proposed BART, t hen the MPCA asks that your BART analysis also identify any regulatory requirements that are triggered. a. Impact analysis part 1: how do I estimate the costs of control? 1. To conduct a cost analysis, you: (1) Identify the emissions units being controlled, (2) Identify design parameters for emission controls, and

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## Page 10 of 24 (3) Develop cost estimates based upon those design parameters. 2. It is important to identify clearly the emission units being cont rolled, that is, to specify a well-defined area or process segment within the plant. In some cases, multiple em ission units can be controlled jointly. However, in other cases, it may be appropriate in the cost analysis to consider whether multiple units will be required to install separate and/or different control devices. The analysis should provide a clear summary list of equipment and the associated control costs. Inadequate documentation of the equipm ent whose emissions are bein g controlled is a potential cause for confusion in comparison of costs of the same controls applie d to similar sources. 3. You then specify the control system design parameters. Potential source s of these design parameters include equipment vendors, background information documents used to support NSPS development, control technique guidelines documents, cost manuals developed by EPA, c ontrol data in trade publications, and engineering and performance test data. The following are a few examples of design parameters for two example control measures:



### ------------------------------------------------------------------------ Control device Examples of design parameters

------------------------------------------------------------------------ Wet Scrubbers............. ............ Type of sorbent us ed (lime, limestone, etc.). Gas pressure drop. Liquid/gas ratio. Selective Catalytic Reduction......... Ammonia to NOX molar ratio. Pressure drop. Catalyst life.

------------------------------------------------------------------------ 4. The value selected for the design parameter should ens ure that the control option will achieve the level of emission control being evaluated. You should incl ude in your analysis documentation of your assumptions regarding design parameters. Examples of supp orting references would include the EPA OAQPS Control Cost Manual (see below) and background information documents used for NSPS and hazardous pollutant emission standards. If the design parameters you specif ied differ from typical designs, you should document the difference by supplying performance test data for t he control technology in question applied to the same source or a similar source. 5. Once the control technology alternatives a nd achievable emissions performance levels have been identified, you then develop estimates of capital and annual costs. The basis for equipment cost estimates also should be documented, either with data supplied by an equipment vendor ( i.e. , budget estimates or bids) or by a referenced source (such as the OAQPS Control Cost Manual, Fifth Edition, February 1996, EPA 453/B–96–001) 14

. In order to maintain and improve consistency, cost estimates should be based on the OAQPS Control Cost Manual, where possible 15 . The Control Cost Manual addresses most control technologies in sufficient detail for a BART analysis. The cost analysis should also take into account any site-specific design or other conditions identified abov e that affect the cost of a particular BART technology option.

14 The OAQPS Control Cost Manual is updated periodically. While th is citation refers to the latest version at the time this guidance was written, you should use the version that is current as of when you conduct your impact analysis. This docum ent is available at the following Web site: http://www.epa.gov/ttn/cat c/dir1/cs1ch2.pdf

.

15 You should include documentation for any add itional information you used for the cost calculations, including any information supplied by vendors that affects your assumptions regarding purchased equipment costs, equipm ent life, replacement of ma jor components, and any other element of the calculatio n that differs from the Control Cost Manual.

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## Page 11 of 24 MPCA note: Please reflect all costs in year 2005 dollars. For EGUs greater than 100 MW, the MPCA requests t hat you use CUECOST to perform cost calculations unless MPCA staff has agreed to the use of an alternativ e method. Please provide a printout of the input & calculation summary used in CUECOST. If you do no t use default values, explain your rationale. b. What do we mean by cost effectiveness? Cost effectiveness, in general, is a criterion used to assess the potential for achieving an objective in the most economical way. For purposes of air pollutant an alysis, “effectiveness” is measured in terms of tons of pollutant emissions removed, and “c ost” is measured in terms of annualized control costs. We recommend two types of cost-effectiveness calculations—average co st effectiveness, and incremental cost effectiveness. c. How do I calculate average cost effectiveness? Average cost effectiveness means the total annualized costs of control divided by annual emissions reductions (the difference between baseline annual emissi ons and the estimate of emissions after controls), using the following formula: Average cost effectiveness (dollars per ton removed) = Control option annualized cost 16

16 Whenever you calculate or report annual costs, y ou should indicate the year for which the costs are estimated. For example, if you use the year 2000 as the basis for cost comparisons, you would report that an annualized cost of $20 millio n would be: $20 million (year 2000 dollars). Baseline annual emissions—Annual emissions with Control option Because you calculate costs in (annualized) dollars per year ($/yr) and because you calculate emissions rates in tons per year (tons/yr), the result is an av erage cost-effectiveness number in (annualized) dollars per ton ($/ton) of pollutant removed.
MPCA Note: Consider “average cost effectiveness” to simply be “cost e ffectiveness,” since the Guidelines do not specify what terms are to be averaged. Use 200 5 dollars for this calculation. To determine the "annualized cost," follow the methodology provided in the EPA AIR PO LLUTION CONTROL COST MANUAL, Sixth Edition (EPA/452/B-02-001, January 2002). Use seven percent as the interest rate in these calculations. Assume a 20 year cont rol equipment life. If a 20 year lif e is not appropriate for the control scenario considered, document your rationale for use of another value.

d. How do I calculate baseline emissions? 1. The baseline emissions rate should represent a real istic depiction of anticipated annual emissions for the source. In general, for the existing sources subjec t to BART, you will estimate the anticipated annual emissions based upon actual emissions from a baseline period. 2. When you project that fu ture operating parameters ( e.g. , limited hours of operation or capacity utilization, type of fuel, raw materials or product mix or type) wi ll differ from past practice, and if this projection has a deciding effect in the BART determi nation, then you must make these parameters or assumptions into enforceable limitations. In the absen ce of enforceable limitations, you calculate baseline emissions based upon continuation of past practice. 3. For example, the baseline emissions calculation for an emergency standby generator may consider the fact that the source owner would not operate more than pa st practice of 2 weeks a year. On the other hand, baseline emissions associated with a base-loaded turbi ne should be based on its past practice which would indicate a large number of hours of operation. This produces a significantly higher level of baseline emissions than in the case of the emergency/standby unit and results in more cost-effective controls. As a

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## Page 12 of 24 consequence of the dissimilar baseline emissions, BART for the two cases could be very different. MPCA Note: To estimate the baseline tons per year for non-EGU, calculate the actual annual emissions based on the highest emissions in 24-consecutive mont hs from January, 1996 to December, 2005 for each of the visibility-impairing pollutants. The baseline emi ssion factor should be correlated to the appropriate operational parameters over this 24-month period. Fo r example, if the baseline NOx emission rate from a furnace is 1000 lb/hour and the maximum number of operating hours over 24- consecutive months was 16,000 hours, then the NOx baseline tons per year for the furnace would be 4000 tons.
For EGU, calculate the baseline annual emissions base d on the highest emissions in 12-consecutive months from January, 2001 to December, 2005 for each of the vi sibility-impairing pollutants. Use CEM data if it is available to determine the highest emissions in 12-cons ecutive months. If CEM data is not available (as for PM10), correlate the baseline emission factor to t he appropriate operational param eters over the 12-month period. For example, if the baseline PM10 emission rate from an EGU is 0.04 lb/MMBtu and the maximum heat input is 5,000,000 MMBtu over a 12-month period, then the PM10 bas eline tons per year would be 100 tons. (This method is based on the PSD baseline calculation method.)

e. How do I calculate incremental cost effectiveness? 1. In addition to the average cost effectiveness of a c ontrol option, you should also calculate incremental cost effectiveness. You should consider the incremental co st effectiveness in combination with the average cost effectiveness when considering whether to eliminate a control option. The incremental cost effectiveness calculation compares the costs and perfo rmance level of a control option to those of the nextmost stringent option, as shown in the following formula (wit h respect to cost per emissions reduction): Incremental Cost Effectiveness (dollars per incremental ton removed) = (Total annualized costs of control option)

− (Total annualized costs of next control option) ÷ (Control option annual emissions)

− (Next control option annual emissions) Example 1: Assume that Option F on Figure 2 has total annualized costs of $1 million to reduce 2000 tons of a pollutant, and that Option D on Figure 2 has total annualized costs of $500,000 to reduce 1000 tons of the same pollutant. The increm ental cost effectiveness of Option F relative to Option D is ($1 million

− $500,000) divided by (2000 tons

− 1000 tons), or $500,000 divided by 1000 tons, which is $500/ton. Example 2: Assume that two control options exis t: Option 1 and Option 2. Option 1 achieves a 1,000 ton/yr reduction at an annualized cost of $1, 900,000. This represen ts an average cost of ($1,900,000/1,000 tons) = $1,900/ton. Option 2 achieves a 980 tons/yr reduction at an annualized cost of $1,500,000. This repres ents an average cost of ($1,500,00 0/980 tons) = $1,531/ton. The incremental cost effectiveness of Option 1 relative to Option 2 is ($1,900,000

− $1,500,000) divided by (1,000 tons

− 980 tons). The adoption of Option 1 instea d of Option 2 results in an incremental emission reduction of 20 tons per year at an add itional cost of $400,000 per year. The incremental cost of Option 1, then, is $20,000 per ton

− 11 times the average cost of $1,900 per ton. While $1,900 per ton may still be deemed reasonable, itis useful to consider both the average and incremental cost in making an ov erall cost-effectiveness finding. Of course, there may be other differences between these options, such as, energy or water use, or non-air environmental effects, which also should be considered in selecting a BART technology. 2. You should exercise care in deriving incremental costs of candidate control opt ions. Incremental costeffectiveness comparisons should focus on annualized cost and emission reduction differences between “dominant” alternatives. To identify dominant alternat ives, you generate a graphical plot of total annualized costs for total emissions reductions for all control alternatives identified in the BART analysis, and by identifying a “least-cost envelope” as shown in Figur e 2. (A “least-cost envelope” represents the set of

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## Page 13 of 24 options that should be dominant in t he choice of a specific option.)

View or download PDF Example: Eight technically feasible control options for analysis are listed. These are represented as A through H in Figure 2. The dominant set of control options, B, D, F, G, and H, represent the least-cost envelope, as we depict by the cost cu rve connecting them. Points A, C and E are inferior options, and you should not use them in calculating incremental cost effectiveness. Points A, C and E represent inferior controls because B will buy more emissions reductions for less money than A; and similarly, D and F will buy more reductions for less money than C and E, respectively. 3. In calculating incr emental costs, you: (1) Array the control options in ascending order of annualized total costs, (2) Develop a graph of the most r easonable smooth curve of the cont rol options, as shown in Figure 2. This is to show the “least-cost envelope” discussed above; and (3) Calculate the incremental cost effectiveness for each dominant option, which is the difference in total annual costs between that option and the next mo st stringent option, divided by the difference in emissions, after controls have been applied, between those two control options. For example, using Figure 2, you would calculate incrementa l cost effectiveness for the difference between options B and D, options D and F, options F and G, and options G and H. 4. A comparison of incremental costs can also be useful in evaluating the viability of a specific control option over a range of efficiencies. For example, depending on the capital and operational cost of a control device, total and incremental cost may vary significantly (either increasing or decreasing) over the operational range of a control device. Also, the great er the number of possible control op tions that exist, the more weight should be given to the incremental costs vs. average costs. It should be noted t hat average and incremental cost effectiveness are identical when only one candidate control option is known to exist.

5. You should exercise caution not to misuse thes e techniques. For example, you may be faced with a choice between two available control devices at a sour ce, control A and control B, where control B achieves slightly greater emission reductions. The average cost(total annual cost/total an nual emission reductions) for each may be deemed to be reasonable. However, the incremental cost (total annual costA – B /total annual emission reductions A – B ) of the additional emission reductions to be achieved by control B may be very great.

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## Page 14 of 24 In such an instance, it may be inappropriate to c hoose control B, based on its hi gh incremental costs, even though its average cost may be considered reasonable. 6. In addition, when you evaluate the average or increm ental cost effectiveness of a control alternative, you should make reasonable and supportable assumptions re garding control efficiencies. An unrealistically low assessment of the emission reduction potential of a certain technology could result in inflated costeffectiveness figures. MPCA Note: The MPCA does not expect that you devel op a least cost envelope such as that shown in the figure. The MPCA expects that t he top-down nature of the BART analysis and the information requested in the analysis will be sufficient for BART determination purposes. f. What other information should I provide in the cost impacts analysis? You should provide documentation of any unusual circumst ances that exist for the source that would lead to cost-effectiveness estimates that would exceed that for rece nt retrofits. This is es pecially important in cases where recent retrofits have cost-effectiveness values t hat are within what has been considered a reasonable range, but your analysis concludes t hat costs for the source being analyz ed are not considered reasonable. (A reasonable range would be a range t hat is consistent with the range of cost effectiveness values used in other similar permit decisions over a period of time.) Example: In an arid region, large amounts of water are needed for a scrubbing system. Acquiring water from a distant location could greatly increas e the cost per ton of emissions reduced of wet scrubbing as a control option. g. What other things are important to consider in the cost impacts analysis? In the cost analysis, you should take care not to focus on incomplete re sults or partial calculations. For example, large capital costs for a control option alone would not preclude selecti on of a control measure if large emissions reductions are projected. In such a case, low or reasonable cost effectiveness numbers may validate the option as an appropriate BART alternative i rrespective of the large capital costs. Similarly, projects with relatively low capital costs may not be cost effective if there are few emissions reduced. h. Impact analysis part 2: How should I analyze and report energy impacts? 1. You should examine the energy requirements of t he control technology and determine whether the use of that technology results in energy penalties or benefit s. A source owner may, for example, benefit from the combustion of a concentrated gas stream rich in vola tile organic compounds; on the other hand, more often extra fuel or electricity is required to power a control device or incinerate a dilute gas stream. If such benefits or penalties exist, they should be quantified to the extentpracticable. Because energy penalties or benefits can usually be quantified in terms of additional cost or income to the source, the energy impacts analysis can, in most cases, simply be factored into the cost im pacts analysis. The fact of energy use in and of itself does not disqualify a technology. 2. Your energy impact analysis should consider only direct energy consumption and not indirect energy impacts. For example, you could estimate the direct en ergy impacts of the contro l alternative in units of energy consumption at the source ( e.g. , BTU, kWh, barrels of oil, tons of coal). The energy requirements of the control options should be shown in terms of total ( and in certain cases, also incremental) energy costs per ton of pollutant removed. Y ou can then convert these units into dollar costs and, where appropriate, factor these costs into the control cost analysis. 3. You generally do not consider indirect energy im pacts (such as energy to produce raw materials for construction of control equipment). However, if you determine, either independently or based on a showing by the source owner, that the indirect energy impact is unusual or significant and that the impact can be well quantified, you may consider the indirect impact.

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## Page 15 of 24 4. The energy impact analysis may also address concer ns over the use of locally scarce fuels. The designation of a scarce fuel may vary from region to region. However, in general, a scarce fuel is one which is in short supply locally and can be better used for alternative purposes, or one which may not be reasonably available to the source either atthe present time or in the near future. 5. Finally, the energy impacts analysis may consider whether there are relative differences between alternatives regarding the use of locally or regionally available coal, and whether a given alternative would result in significant economic disruption or unemployme nt. For example, where two options are equally cost effective and achieve equivalent or similar emissi ons reductions, one option may be preferred if the other alternative results in significant disruption or unemployment. MPCA Note: Please report energy impacts on a $ per t on of pollutant removed basis. Please document all assumptions made in calculating energy costs. i. Impact analysis part 3: How do I analyze “non-air quality environmental impacts?” 1. In the non-air quality related environmental impacts portion of the BART analysis, you address environmental impacts other than air quality due to em issions of the pollutant in question. Such environmental impacts include solid or hazardous wast e generation and discharges of polluted water from a control device. 2. You should identify any significant or unusual enviro nmental impacts associated with a control alternative that have the potential to affect t he selection or elimination of a c ontrol alternative. Some control technologies may have potentially significant secon dary environmental impacts. Scrubber effluent, for example, may affect water quality and land use. Alternat ively, water availability may affect the feasibility and costs of wet scrubbers. Other examples of secondar y environmental impacts could include hazardous waste discharges, such as spent catalysts or contaminated carbon. Generally, these types of environmental concerns become important when sensitive site-specificreceptors exist or when the incremental emissions reductions potential of the more st ringent control is only marginally greater than the next most-effective option. However, the fact that a control device creates liquid and solid wa ste that must be disposed of does not necessarily argue against selection of that technol ogy as BART, particularly if the control device has been applied to similar facilities elsewhere and the solid or liquid waste is similar to those other applications. On the other hand, where you or t he source owner can show that unusual circumstances at the proposed facility create greater problems than experienced elsewher e, this may provide a basis for the elimination of that control alternative as BART. 3. The procedure for conducting an analysis of non-air quality environmental impacts should be made based on a consideration of site-specific circumstances. If you propose to adopt the moststringent alternative, then it is not necessary to perform this analysis of environmental impacts for the entire list of technologies you ranked in Step 3. In general, the analysis need only addr ess those control alternatives with any significant or unusual environmental impacts that hav e the potential to affect the select ion of a control alternative, or elimination of a more stringent cont rol alternative. Thus, any important relative environmental impacts (both positive and negative) of alternativ es can be compared with each other. 4. In general, the analysis of impacts starts with the identification and quan tification of the solid, liquid, and gaseous discharges from the control device or devic es under review. Initially, you should perform a qualitative or semi-quantitat ive screening to narrow the analysis to discharges with potential for causing adverse environmental effects. Next, you should a ssess the mass and composition of any such discharges and quantify them to the extent possible, based on readil y available information. You should also assemble pertinent information about the public or environm ental consequences of releasing these materials. j. Impact analysis part 4: What are examples of non-air quality environmental impacts? The following are examples of how to conduct non-air quality environmental impacts: (1) Water Impact

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## Page 16 of 24 You should identify the relative quantities of water used and water pollutants produced and discharged as a result of the us e of each alternative emission cont rol system. Where possible, you should assess the effect on ground water and such local surface water quality parameters as ph, turbidity, dissolved oxygen, salinity, toxic chemic al levels, temperature, and any other important considerations. The analysis coul d consider whether applicable water quality standards will be met and the availability and effectiveness of various te chniques to reduce potential adverse effects. (2) Solid Waste Disposal Impact You could also compare the quality and quantity of solid waste ( e.g. , sludges, solids) that must be stored and disposed of or recycled as a result of the application of each al ternative emission control system. You should consider the composition and various other characteristics of the solid waste (such as permeability, water retention, rewateri ng of dried material, compression strength, leachability of dissolved ions, bulk density, abilit y to support vegetation growth and hazardous characteristics) which are significant with regard to potential surface water pollution or transport into and contamination of subsurfa ce waters or aquifers. (3) Irreversible or Irretrievabl e Commitment of Resources You may consider the extent to which the alter native emission control systems may involve a tradeoff between short-term environmental gains at the expense of long-term environmental losses and the extent to which the alternative systems may resultin irreversible or irretrievable commitment of resources (for example, use of scarce water resources). (4) Other Adverse Environmental Impacts You may consider significant differences in noise le vels, radiant heat, or dissipated static electrical energy of pollution control alternatives. Other examples of non-air quality environmental impacts would include hazardous waste discharges such as spent catalysts or contaminated carbon. k. How do I take into account a pr oject's “remaining useful life” in calculating control costs? 1. You may decide to treat the requirement to consider the source's “remaining useful life” of the source for BART determinations as one element of t he overall cost analysis. The “remaini ng useful life” of a source, if it represents a relatively short time period, may affect t he annualized costs of retrofitcontrols. For example, the methods for calculating annualized costs in EPA's OAQPS Control Cost Manual require the use of a specified time period for amortization that varies based u pon the type of control. If the remaining useful life will clearly exceed this time period, the remaining useful life has essentially no e ffect on control costs and on the BART determination process. Wher e the remaining useful life is less than the time period for amortizing costs, you should use this shorter ti me period in your cost calculations. MPCA Note: For units being evaluated in the OAQPS C ontrol Cost Manual, any time period that is less than the lifetime of the cont rol equipment set in the Control Cost Manual , e.g., the remaining life of the equipment, should be supported with a rationale that includes an a ssessment of why it is not reasonable to assume the facility will maintained or reconstructed for continue d operation, thus allowing the control equipment to be used for an extended period. 2. For purposes of these guidelines, the remain ing useful life is the difference between: (1) The date that controls will be put in place (capital and other c onstruction costs incurred before controls are put in place ca n be rolled into the first year, as suggested in EPA's OAQPS Control Cost Manual ); you are conducting the BART analysis; and (2) The date the facility permanentlystops operations. Where this affects the BART determination, this date should be assured by a federally- or State-enforceable restrict ion preventing further

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## Page 17 of 24 operation. 3. We recognize that there may be situations where a source operator in tends to shut down a source by a given date, but wishes to retain the flexibility to c ontinue operating beyond that date in the event, for example, that market conditions c hange. Where this is the case, your BART analysis may account for this, but it must maintain consistency with the statutory r equirement to install BART within 5 years. Where the source chooses not to accept a federally enforceable co ndition requiring the source to shut down by a given date, it is necessary to determine whether a reduced time period for the remaining useful life changes the level of controls that would have been required as BART. If the reduced time period does change the level of BART controls, you may identify, and include as part of the BART emission limitation, the more stringent level of control that would be required as BART if there were no assumption that reduced the remaining useful life. You may incorporate into the BART emission limit this more stringent level, which would serve as a contingency should the source continue operating more than 5 years after the date EPA approves the rele vant SIP. The source would not be allowed to operate after the 5-year mark without such controls. If a source does operate after the 5-year mark without BART in place, the source is considered to be in violation of the BART emissions limit for each day of operation. 5. Step 5: How should I determine visibility impacts in the BART determination? The following is an approach you may use to determine visi bility impacts (the degree of visibility improvement for each source subject to BART) for the BART determinat ion. Once you have determined that your source or sources are subject to BART, you must conduct a visi bility improvement determination for the source(s) as part of the BART determination. When making this determi nation, we believe you have flexibility in setting absolute thresholds, target levels of improvement, or de minimis levels since the deciview improvement must be weighed among the five factors, and you are free to determine the weight and significance to be assigned to each factor. For example, a 0.3 deciview improvement may merit a strong er weighting in one case versus another, so one “bright line” may not be appropriate. [Note that if sources have elected to apply the most stringent controls available, consiste nt with the discussion in section E. step 1. below, you need not conduct, or require the source to conduct, an air quality modeling analysis for the purpose of determining its visibility impacts.]

Use CALPUFF 17 , or other appropriate dispersion model to determine the visibility improvement expected at a Class I area from the potential BART control technologyapplied to the source. Modeling should be conducted for SO 2 , NO X , and direct PM emissions (PM 2.5 and/or PM 10 ). If the source is making the visibility determination, you should review and approve or di sapprove of the source's analysis before making the expected improvement determination. There are several steps for determining the visibility impacts from an individual source using a dispersion model:

17 The model code and its documentation are av ailable at no cost for download from http://www.epa.gov/scram 001/tt22.htm#calpuff

. • Develop a modeling protocol. Some critical items to include in a modeling protocol are meteorological and terrain data, as well as sourcespecific information (stack height, temperature, exit ve locity, elevation, and allowable and actual emission rates of applicable pollutants), and receptor data from appropriate Class I areas. We recommend following EPA's Interagency Workgroup on Air Quality Mode ling (IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long Range Transport Impacts 18 for parameter settings and meteorological data inputs; the use of other settings from those in IWAQM should be identified and explained in the protocol.

18 Interagency Workgroup on Air Quality Model ing (IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long Range Transport Impacts, U.S. Environmental Protection Agency, EPA–454/R–98–019, December 1998. One important element of the protocol is in establishing the receptors that will be used in the model. The

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## Page 18 of 24 receptors that you use should be located in the neares t Class I area with sufficient density to identify the likely visibility effects of the source. For other Class I areas in relatively close proximity to a BART-eligible source, you may model a few strategic receptors to det ermine whether effects at those areas may be greater than at the nearest Class I area. For example, you might chose to locate receptors at these areas at the closest point to the source, at the highest and lowest elevation in the Class I area, at the IMPROVE monitor, and at the approximate expected plume release height. If the highest modeled effects are observed at the nearest Class I area, you may choose not to analyze the other Class I areas any further as additional analyses might be unwarranted. You should bear in mind that some receptors within the relevant Class I area may be less than 50 km from the source while other receptors within that same Class I area may be greater than 50 km from the same source. As indicated by the Guideline on Air Quality Models, this situation may call for the use of two different modeling approaches for the same Class I area and source, depending upon the State's chosen method for modeling sources less than 50 km. In situat ions where you are assessing visibility impacts for source-receptor distances less than 50 km, you should us e expert modeling judgment in determining visibility impacts, giving consideration to bot h CALPUFF and other EPA-approved methods. In developing your modeli ng protocol, you may want to consult with EPA and your regional planning organization (RPO). Up-front consultation will ensur e that key technical issues are addressed before you conduct your modeling. MPCA Note: For determining visibility impacts of the va rious control alternatives, use the modeling protocol developed by the MPCA titled “BART Modeling Protocol to Determine Sources Subject-to-BART and for BART Determinations in the State of Minnesota, Final Draft, <insert date>”. It is available at: http://www.pca.state.mn.u s/air/regionalhaze.html <Note this document has not yet been finalized which means it has not been approved by EPA as part of the regi onal haze SIP. The specific emissions and stack parameter inputs used for each facility in the s ubject-to-BART modeling will be available at http://www.pca.state.mn.us /air/regionalhaze.html . The Final Draft version should be available in February, 2006> If you did not estimate PM2.5 emissions in the Request for Information spreadsheet to identify BART-eligible sources, then the MPCA estimated a maximum 24-hour average actual PM2.5 emission rate using the PM10 The MPCA estimated PM2.5 by scaling the PM10 emissions to PM2.5 using the PM2.5/PM10 ratio calculated by the MPCA for the 2002 emissions inv entory. To quantify PM2.5 emissions in the 2002 emissions inventory, the MPCA used three different method s: 1) If the facility didn’t submit PM10 stack test data, MPCA estimated both the PM2.5 and PM10 primary emissions (filterable +condensable) using uncontrolled emission factors from EPA’ s FIRE database and appl ying MPCA default control efficiencies; 2) If the facility did submit PM10 stack test data, MPCA estimated the PM2.5 by scal ing the existing ration of PM2.5/PM10 primary emissions derived fr om method #1; or 3) If the facility’s SCC were not available in FIRE, MPCA estimated the PM2.5 using EPA’s PM Calculator http://www.epa.gov/ttn/chief/s oftware/pmca lc/index.html
Thus, PM2.5 emissions will be the scale d PM2.5 (fine PM) and the remainder (PM 2.5-10 ) will be assigned to PM10 (coarse PM). It is possible the PM2.5/PM10 ratio for the control alternative will not be the same as the base case ratio. If the ratio will not be the same, it is recommended that you use the method used by the MPCA to estimate PM2.5 emissions for the various c ontrol alternatives evaluat ed. Don Sheperd of the National Park Service has developed PM10 speciation methods for various emission units (large coal-fired boilers, thermal dryers, oil boilers, and cement kilns) with control applied. If you have a BART-eligible emission unit for which PM10 speciation data is available, then you may us e that method instead. <These methods are still under development and not yet available on-line. Contact Don Sheperd at don shepherd@nps.gov , if you would like the most recent drafts.> If speciation data fo r particulate matter emissions is available from stack testing, then such speciation may be used in the modeling provided the basis for speciation is documented. Please consult with MPCA staff if you plan to use stack test data to speciate particulate matter for modeling purposes. • For each source, run the model, at pre-control and post-control emission rates according to the accepted methodology in the protocol.

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## Page 19 of 24 Use the 24-hour average actual emission rate from the highest emitting day of the meteorological period modeled (for the pre-control scenario). Calculate t he model results for each receptor as the change in deciviews compared against natural visibility conditi ons. Post-control emission rates are calculated as a percentage of pre-control emission rate s. For example, if the 24-hr pre- control emission rate is 100 lb/hr of SO 2 , then the post control rate is 5 lb/hr if the control efficiency being evaluated is 95 percent.

MPCA Note: Provide tables with the pre-control and pos t-control inputs used for the modeling runs. See the suggested format in Attachment 3.

• Make the net visibility im provement determination. Assess the visibility improvement based on the modeled ch ange in visibility impacts for the pre-control and post-control emission scenarios. You have flexibility to assess visibility improvements due to BART controls by one or more methods. You may consider the frequency, magnitude, and duration components of impairment. Suggestions for making the determination are: • Use of a comparison threshold , as is done for determining if BART-eligible sources should be subject to a BART determination. Comparison thresholds can be us ed in a number of ways in evaluating visibility improvement ( e.g., the number of days or hours that the thre shold was exceeded, a single threshold for determining whether a change in impacts is significan t, or a threshold representing an x percent change in improvement). MPCA Note: The MPCA will not be providing you with a comparison threshold for evaluating visibility improvement. The MPCA does not believe that the degree of visibility improvement should be contingent upon perceptibility. This approach is consistent with EPA’s Guidelines and EPA’s subsequent clarification of the Guidelines. In its Guidelines, EPA did not recommend a deciview threshold for states to use in evaluating the degree of visibility improvement factor for a BART determination. • Compare the 98th percent days for the pre- and post-control runs. Note that each of the modeling opt ions may be supplemented with source apportionment data or source apportionment modeling. MPCA Note: See Attachment 3 for the MPCA’s sugg ested format to use in providing results of the 98 th percentile days for the pre- and post-control runs for eac h of the model years as well as the combination of all three model years. In addition, the MPCA is asking that you report t he number of days above 0.5 deciview for each of the three model years as well as t he combination of all three model years. The use of 0.5 is not intended as a threshold, but merely anot her metric by which to understand visibility modeling results. E. How do I select the “best” alternative, using the results of Steps 1 through 5? 1. Summary of the Impacts Analysis From the alternatives you evaluated in Step 3, we re commend you develop a chart (or charts) displaying for each of the alternatives: (1) Expected emission rate (tons per year, pounds per hour); (2) Emissions performance level ( e.g. , percent pollutant removed, emissions per unit product, lb/MMBtu, ppm);

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## Page 20 of 24 (3) Expected emissions reductions (tons per year); (4) Costs of compliance—total annualized costs ($), cost effectiveness ($/ton), and incremental cost effectiveness ($/ton), and/or any other cost-e ffectiveness measures (such as $/deciview); (5) Energy impacts; (6) Non-air quality environmental impacts; and (7) Modeled visibility impacts. 2. Selecting a “best” alternative

1. You have discretion to determine the order in wh ich you should evaluate control options for BART. Whatever the order in which you choose to evaluate options, you should always (1) display the options evaluated; (2) identify the average and incremental costs of each option; (3 ) consider the energy and non-air quality environmental impacts of each option; (4) consi der the remaining useful life; and (5) consider the modeled visibility impacts. You should provide a justif ication for adopting the technology that you select as the “best” level of control, including an explanation of the CAA factors thatled you to choose that option over other control levels. MPCA Note: The MPCA would like you to use a top-down approach to evaluate control strategies. If you determine that the most st ringent alternative in the ranking d oes not impose unreasonable costs of compliance, taking into account both average and in cremental costs, the analysis begins with the presumption that this level is selected. Under this, you would then proceed to consider whether energy and non-air quality environmental impacts would justify selecti on of an alternative control option. If there are no outstanding issues regarding energy and non-air qual ity environmental impacts, the analysis is ended and the most stringent alternative is identif ied as the “best system of continuous reduction.” If you determine that the most stringent alternative is unacceptable due to such impacts, this approach would require you to document the rationale for this finding. Then, the next most effective alternative in the listing becomes the new control candidate and is similarly evaluated. Th is process continues until you identify a technology which does not pose unacceptable costs of compliance, energy and/or non-air quality environmental impacts. MPCA staff will be available to work with you dur ing your BART analysis preparation to address your questions and concerns, such as the specific concern that a particular technology favored by you would be eliminated under a top-down approach. In making the BART determination itself, all factors will be considered, including the degree of visibility improvement.
2. In the case where you are conducting a BART det ermination for two regulated pollutants on the same source, if the result is two different BART technolo gies that do not work we ll together, you could then substitute a different technology or combination of technologies. 3. In selecting a “best” alternative, shoul d I consider the affordability of controls? 1. Even if the control technology is cost effect ive, there may be cases where the installation of controls would affect the viability of continued plant operations. 2. There may be unusual circumstanc es that justify taking into cons ideration the conditions of the plant and the economic effects of requiring the use of a given control technology. These effects would include effects on product prices, the market share, and profitability of the source. Where there are such unusual circumstances that are judged to affect plantoperations, you may take into consideration the conditions of t he plant and the economic effects of requiring the use of a control technology. Where these effects are judged to have a severe impact on plant operations you may consider them in the selection process, but you may wish to pr ovide an economic analysis that demonstrates, in sufficient detail for public revi ew, the specific economic effects, parameters, and reasoning. (We recognize that this review proc ess must preserve the c onfidentiality of sensitive business information). Any analysis may also cons ider whether other competing plants in the same

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## Page 21 of 24 industry have been required to install BART controls if this information is available. 4. Sulfur dioxide limits for utility boilers You must require 750 MW power plants to meet specific control levels for SO 2 of either 95 percent control or 0.15 lbs/MMBtu, for each EGU greater than 200 MW that is currently unc ontrolled unless you determine that an alternative control level is justified based on a carefu l consideration of the stat utory factors. Thus, for example, if the source demonstrates circumstances affecting its ability to cost-effectively reduce its emissions, you should take that into account in deter mining whether the presumptiv e levels of control are appropriate for that facility. For a currently uncontroll ed EGU greater than 200 MW in size, but located at a power plant smaller than 750 MW in size, such controls are generally cost-effective and could be used in your BART determination considering the five factors specified in CAA section 169A(g)(2). While these levels may represent current control capabilities, we expect t hat scrubber technology will continue to improve and control costs continue to decline. You should be sure to consider the level of contro l that is currently best achievable at the time that you are conducting your BART analysis. For coal-fired EGUs with existing post-combustion SO 2 controls achieving less than 50 percent removal efficiencies, we recommend that you evaluate construc ting a new FGD system to meet the same emission limits as above (95 percent removal or 0.15 lb/mmBtu ), in addition to the evaluation of scrubber upgrades discussed below. For oil-fired units, regardless of size, you should evaluate limiting the sulfur content of the fuel oil burned to 1 percent or less by weight. For those BART-eligible EGUs with pre-existing post-combustion SO 2 controls achieving removal efficiencies of at least 50 percent, your BART determination should consider cost effective scrubber upgrades designed to improve the system's overall SO 2 removal efficiency. There are numerous scrubber enhancements available to upgrade the average removal efficiencies of all types of existing scrubber systems. We recommend that as you evaluate the definition of “upgr ade,” you evaluate options that not only improve the design removal efficiency of the scrubber vessel itsel f, but also consider upgrades that can improve the overall SO 2 removal efficiency of the scrubber system. In creasing a scrubber system's reliability, and conversely decreasing its downtime, by way of optim izing operation procedures, improving maintenance practices, adjusting scrubber chemistry, and increasi ng auxiliary equipment redundancy, are all ways to improve average SO 2 removal efficiencies. We recommend that as you evaluate the performance of existing wet scrubber systems, you consider some of the following upgrades, in no particular order, as potential scrubber upgrades thathave been proven in the industry as cost effective means to increase overall SO 2 removal of wet systems: (a) Elimination of Bypass Reheat; (b) Installation of Liquid Distribution Rings; (c) Installation of Perforated Trays; (d) Use of Organic Acid Additives; (e) Improve or Upgrade Scrubber Auxiliary System Equipment; (f) Redesign Spray Header or Nozzle Configuration. We recommend that as you evaluate upgrade options for dry scrubber systems, you should consider the following cost effective upgrades, in no particular order: (a) Use of Performance Additives;

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## Page 22 of 24 (b) Use of more Reactive Sorbent; (c) Increase the Pulverization Level of Sorbent; (d) Engineering redesign of atomizer or slurry injection system. You should evaluate scrubber upgrade options based on the 5 step BART analysis process. 5. Nitrogen oxide limits for utility boilers You should establish specific numerical limits for NO X control for each BART determination. For power plants with a generating capacity in excess of 750 MW curr ently using selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR) for part of t he year, you should presume that use of those same controls year-round is BART. For other sources currently using SCR or SNCR to reduce NO X emissions during part of the year, you should carefully consider requiring the use of these controls year-round as the additional costs of operating the equipment throughout the year would be relatively modest. For coal-fired EGUs greater than 200 MW located at greater than 750 MW power plants and operating without post-combustion controls ( i.e., SCR or SNCR), we have provided presumptive NO X limits, differentiated by boiler design and type of coal burned. You may determine that an alternative control level is appropriate based on a careful considerat ion of the statutory factors. Fo r coal-fired EGUs greater than 200 MW located at power plants 750 MW or less in size and operating without post-combustion controls, you should likewise presume that these sa me levels are cost-effective. You should require such utility boilers to meet the following NO X emission limits, unless you determine thatan alternative control level is justified based on consideration of the stat utory factors. The following NO X emission rates were determined based on a number of assumptions, including that the EGU boiler has enough volume to allow for installation and effective operation of separated overfire air ports. For boilers where these assumptions are incorrect, these emission limits may not be cost-effective.

Table 1_Presumptive NOX Emission Limits for BART-Eligible Coal-Fired Units 19

--------------------------------------------------------------------------------------------------------------------- NOX presumptive Unit type Coal type limit (lb/ mmbtu) 20

--------------------------------------------------------------------------------------------------------------------- Dry-bottom wall-fired......... Bituminous ............ 0.39 Sub-bituminous........ 0.23 Lignite............... 0.29 Tangential-fired.............. Bituminous............ 0.28 Sub-bituminous........ 0.15 Lignite............... 0.17 Cell Burners.................. Bituminous...... ...... 0.40 Sub-bituminous........ 0.45 Dry-turbo-fired............... Bituminous............ 0.32 Sub-bituminous........ 0.23 Wet-bottom tangential-fired... Bitumin ous............ 0.62

------------------------------------------------------------------------ 19 No Cell burners, dry-turbo-fired units, nor wet-bottom tangential- fired units burning lignite were identified as BART-eligible, thus no presumptive limit was determined. Similarly, no wet-bottom tangential- fired units burning sub-bituminous were identified as BART-eligible. 20 These limits reflect the design and technological assumptions discussed in the technical support document for NOX limits for these guidelines. See Technical Support Document for BART NOX Limits for Electric Generating Units and Technical Support Document for BART NOX Limits for Electric Generating Un its Excel Spreadsheet, Memorandum to Docket OAR 2002-0076, April 15, 2005.

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## Page 23 of 24 Most EGUs can meet these pres umptive NOX limits thr ough the use of current combustion control technology, i.e. the careful control of combustion air a nd low-NOX burners. For units that cannot meet these limits using such technologies, you should consider whether advanced combustion control technologies such as rotating opposed fire air should be used to meet these limits. Because of the relatively high NOX emission rates of cyclone units, SCR is more cost-effective than the use of current combustion control technology for these units. The use of SCRs at cyclone units burning bituminous coal, sub-bituminous coal, and lignite should enable the units to cost-e ffectively meet NOX rates of 0.10 lbs/mmbtu. As a result, we are establishing a presumptive NOX limit of 0.10 lbs/mmbtu based on the use of SCR for coal-fired cyclone units greater than 200 MW located at 750 MW power plants. As with the other presumptive limits established in this guideline, you may determine thatan alternative level of control is appropriate based on your consideration of the relevant statutory factors. For other cyclone units, you should review the use of SCR and consider whether these pos t-combustion controls should be required as BART. For oil-fired and gas-fired EGUs larger than 200MW, we be lieve that installation of current combustion control technology to control NOX is generally highly cost-e ffective and should be considered in your determination of BART for these sources. Many such units can make significant reductions in NOX emissions which are highly cost-effective through the applicatio n of current combustion control technology 21
21 See Technical Support Document for BART NO X Limits for Electric Generating Units and Technical Support Document for BART NOX Limits for Electric Generating Units Excel Spreadsheet, Memorandum to Docket OAR 2002–0076, April 15, 2005. MPCA Note: While the MPCA has not yet made the dete rmination that CAIR substitutes for BART, we would like you to conduct a BART analysis for CAIR EGU at your facility that the MPCA has determined contribute to visibility impairment in a Class I area. We would like the analysis to include an evaluation of technology to reduce emissions to at least presumptiv e BART levels regardless of EGU size. V. Enforceable Limits/Compliance Date To complete the BART process, you must establish enforceable emission limits that reflect the BART requirements and require compliance within a given peri od of time. In particular, you must establish an enforceable emission limit for each subject emission unitat the source and for each pollutant subject to review that is emitted from the source. In additi on, you must require compliance with the BART emission limitations no later than 5 years after EPA approves your regional haze SIP. If technological or economic limitations in the application of a measurement methodology to a particular emission unit make a conventional emissions limit infeasible, you may in stead prescribe a design, equipment, work practice, operation standard, or combination of these types of standards. You should consider allowing sources to “average” emissions across any set of BART-eligible em ission units within a fenceline, so long as the emission reductions from each pollutant being contro lled for BART would be equal to those reductions that would be obtained by simply controlling each of the BART-e ligible units that constitute BART-eligible source. You should ensure that any BART requirements are wri tten in a way that clearly specifies the individual emission unit(s) subject to BART regulation. Bec ause the BART requirements themselves are “applicable” requirements of the CAA, they must be included as title V permit conditions according to the procedures established in 40 CFR part 70 or 40 CFR part 71. Section 302(k) of the CAA requires emissions limit s such as BART to be met on a continuous basis. Although this provision does not necessarily require the use of continuous emissions monitoring (CEMs), it is important that sources employ techniques that ensure compliance on a continuous basis. Monitoring requirements generally applicable to sources, includi ng those that are subject to BART, are governed by other regulations. See, e.g., 40 CFR part 64 (compl iance assurance monitoring); 40 CFR 70.6(a)(3) (periodic monitoring); 40 CFR 70.6(c)(1) (sufficiency monitoring). Note also that while we do not believe that CEMs would necessarily be required for all BART sources, the vast majority of electric generating units potentially subject to BART already employ CEM technology for other programs, such as the acid rain program. In addition, emissions limits must be enforceable as a practical matter (contain appropriate averaging times,

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## Page 24 of 24 compliance verification procedures and recordkeeping re quirements). In light of the above, the permit must: • Be sufficient to show compliance or noncomplia nce (i.e., through monitoring times of operation, fuel input, or other indices of o perating conditions and practices); and • Specify a reasonable averaging time consistent with established reference methods, contain reference methods for determining compliance, and provide for adequate reporting and recordkeeping so that air quality agency personn el can determine the comp liance status of the source; and • For EGUS, specify an averaging time of a 30-day ro lling average, and contai n a definition of “boiler operating day” that is consistentwith the definition in the propos ed revisions to the NSPS for utility boilers in 40 CFR Part 60, subpart Da. 22. You should consider a boiler operating day to be any 24- hour period between 12:00 midnight and the following midnight during which any fuel is combusted at any time at the steam generating unit. This would allow 30-day rolling average emission rates to be calculated consistently across sources. MPCA Note: While the MPCA will determine the compliance date and emission limit, we encourage you to suggest a compliance schedule and to propose a BAR T limit consistent with the above guidance The MPCA will allow you to “average” emissions across any set of BART-eligible emission units within a fenceline, so long as facility-wide emission reduction s from each pollutant being controlled for BART would be equal or greater than those reductions expected by simp ly controlling each of the BART-eligible units at a BART-eligible source.

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